The results were issued by the Department for Education on Thursday and showed most Islington secondary schools fell below the England average for GCSE attainment and all but one were worse than average for A-level results.

The worst performer was the controversial City of London Academy Islington, in Prebend Street, Islington, where just 31 per cent of GCSE pupils got the benchmark five A* to C grades including English and maths in 2011 – a huge 12 per cent fall on 2010 and making it one of only 107 schools in England to miss the government’s minimum target of 35 per cent.

Holloway School in Hilldrop Road, Holloway, scraped above the target with 36 per cent and drops in grades were also seen at Central Foundation for Boys, in Cowper Street, Finsbury and at Elizabeth Garrett Anderson in Donegal Street, Islington.

The school-by-school breakdown exposes the full picture behind October’s news that Islington had the worst average GCSE grades in London – with only 49 per cent of pupils getting five good GCSEs, as standards dropped for the first time in years from 50 per cent in 2010.

Cllr Richard Watts, Islington Council’s executive member for children and families, said the poor results were partly down to a “difficult cohort”. He said: “A number of our schools had quite a difficult GCSE cohort that had low achievement going into secondary school. I’m very confident we will see a rise again next year.”

There was some good news, with big improvements at both Highbury Fields School in Highbury Hill, Highbury and Mount Carmel Technology College in Holland Walk, Archway.

St Aloysius College in Hornsey Lane, Archway, topped the GCSE table with 74 per cent of students reaching the benchmark, while St Mary Magdalene Academy in Liverpool Road, Holloway, had far and away the best average A-level point score per pupil at 1,022.9 – the only college in Islington above the England average of 728.2.

Cllr Watts added: “Schools such as Highbury Fields have improved enormously and that shows how successful Islington schools can be. I think the results show there are lots of very good things happening in our schools, but clearly there’s too much variability between their performance.

“We were disappointed by the results in English and maths. We had too many kids getting Ds in English in particular, which brought down the results hugely. A few grades different and things would have looked much better.”

Cllr Terry Stacy, leader of the Liberal Democrat opposition, said he hopes the fall in GCSE grades was just a blip in the long-term trend of improvement.

Just goes to show what everybody already knows. Islington state schools are a death sentence as far as employability and social mobility are concerned. Always have been, always will be, avoid at all costs.